1. Field of the Invention
The present invention relates to a method for designing a mold in the case of injection molding of resin, a program for making a computer carry out the process of injection molding, a method for producing an injection molding that produces the injection molding using the mold, and an injection molding device.
2. Related Background Art
In injection molding, a plurality of gates are required depending on the size and the shape of a is product. In this case, as described below, there have been made proposals of improvement in molding process aspect or in product quality aspect, such as reduction in necessary mold clamping force and weld line position control, through controlling the state of flow of the molten material inflow through the gates.
For example, Japanese Patent Laid-open Gazette No. 2002-355866, page 2 discloses, in the case where the product shape extends in a longitudinal direction, that a plurality of gates through which molten resin is injected into the cavity are arranged along the direction from the resin filling starting side to the filling completion side, and the molten resin is sequentially injected into the cavity at a specified interval starting with the injection at the filling starting gate, thereby to reduce a mold clamping force required for molding.
Also Japanese Patent Laid-open Gazette No. Heisei 8-118420, pages 2 and 3 describes the prevention of weld line occurrence by injecting a softened resin material from the second gate into the cavity at almost the same time when the resin is injected from the first gate passes over the second gate, or after the resin is injected from the first gate passes over the second gate.
Further, Japanese Patent Laid-open Gazette No. 2001-277308, pages 7 to 9 discloses a technology to predict the location of weld lines generated in a molding through flow simulation of a molding process by dividing the shape of the molding into fine elements, further by adjusting the open or close of valve gates on the basis of thus predicted weld lines to shift the weld lines to a preferable modified location.